Sustainable Production of Stable Lignin Nanoparticle-Stabilized Pickering Emulsions via Cellulose Nanofibril-Induced Depletion Effect

Spherical lignin nanoparticles (SLNs) are able to formulate Pickering emulsions with various applications. However, SLN-stabilized emulsions commonly comprise droplets in the micron range, resulting in inevitable instability upon storage. Herein, nonadsorbing cellulose nanofibrils (CNF) are shown to induce stabilization of the diluted SLN-stabilized Pickering emulsions via concentration-dependent depletion effects. Two regimes for such depletion interactions are established, including depletion flocculation-induced droplet aggregation at intermediate CNF concentrations and depletion stabilization of micron-sized droplets over critical CNF concentrations (0.2 wt %). The long-term stability of the SLN-based emulsions against creaming is over two months. The universality of the findings is tested with different initial oil volume fractions and droplet diameters. Overall, this study unveils the depletion effects in SLN-stabilized Pickering emulsions induced by renewable CNF, offering a simple, sustainable route for tailoring their phase behavior and creating ultrastable systems that are available for formulating green products.